1. Field of the Invention
This invention generally relates to methods and apparatuses for encoding particles and, more specifically, to methods and systems for altering fluorescent intensities of a plurality of particles.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Spectroscopic techniques are widely employed in the analysis of chemical and biological systems. Most often, these techniques involve measuring the absorption or emission of electromagnetic radiation by the material of interest. One application is in the field of microarrays, which is a technology exploited by a large number of disciplines including the combinatorial chemistry and biological assay industries. Luminex Corporation of Austin, Tex. has developed systems in which biological assays, for example, are performed on the surface of variously colored fluorescent particles. In such systems, a multiplexing scheme is often employed in which multiple analytes are evaluated in a single sample. To facilitate a multiplexing scheme, particles are often configured into distinguishable groups. For instance, different fluorescent dyes as well as different concentrations of dyes may be absorbed into particles and/or bound to the surface of particles. In one example, employing two dyes at 10 different concentrations among a set of particles produces 100 fluorescently distinguishable particle categories. The number of particle categories may be augmented by increasing the number of dyes and/or different dye intensities. For example, if 15 different dye intensities were possible rather than 10 in the aforementioned example, then 225 particle categorizations would be achievable. The inclusion of additional dyes and/or dye intensities, however, adds complexity to the system, which can greatly contribute to increasing the expense and/or difficulty of producing the platform.
In any case, dyes are generally chosen based on their ability to emit light at a wavelength of a selected detection window. The detection windows define the different particle categories and are typically spaced apart by a certain number of wavelengths. In general, the dyes are designed to minimize the overlap of a dye's fluorescent signal within adjacent windows. In this manner, the different particle categorizations may be sufficiently distinguishable. In some cases, however, it may be difficult to produce particles exhibiting fluorescent intensities which fall into predetermined detection windows. As such, it may theoretically possible to produce hundreds of particle categories, but in practice such a number of categories is difficult to achieve. One factor that may limit the number of particle categories that can be produced may be the controllability of the methods used to dye the particles (e.g., how well variations of the process parameters of the methods can be minimized, the predictability of the methods to produce dyed particles of particular fluorescent intensities, and the degree to which parameters of the methods can be altered to produce desired fluorescence emissions). Furthermore, dyed particles may not exhibit expected fluorescence emissions for a number of other reasons including varying characteristics (e.g., size and/or composition) of the particles prior to being dyed. In any case, particles that exhibit fluorescence emissions that do not fit within a selected detection window are typically scrapped or discarded, increasing the time and expense of producing a population of particles for a multiplexing scheme.
Accordingly, it would be advantageous to develop methods and systems for altering fluorescence emissions of dyed particles. Such methods and systems may be particularly beneficial for encoding particles with specific fluorescent intensities and/or adjusting the fluorescent intensity of a particle which does not fall within a predetermined detection window.